Cosmos #2 - One Voice in the Cosmic Fugue

What's a Fugue?

A fugue is a musical piece in which several overlapping variations on a theme are
played simultaneously by different sections of an orchestra. Each section is called a
"voice." The overall effect suggests rapid flight, hence the term. The word
"fugue" comes from the same root as our word "fugitive."

At the risk of offending serious music lovers, the general idea of a fugue is similar
to the familiar round singing of "Row, Row, Row Your Boat", except that in a
round, each voice simply repeats the same theme over and over ... and over ... and over...
In a fugue, the theme is continuously varying and the overall organization is far more
complex.

Sagan likens the possible variations of life in the Universe to a fugue in which each
voice (planet) is playing its own variations on the main theme. So where's the fugue in
this episode? Although there is some Baroque-sounding music, ironically, there is no
fugue anywhere in the music in this episode!

Evolution by Natural Selection

"Evolution is a Fact, Not a Theory - It Really Happened"

Here's Sagan at his in-your-face best. A lot of people, of course, are opposed to
evolution on religious or ideological grounds, and try to maintain some intellectual
"wiggle room" that allows them to deny evolution. Sagan takes one of the most
widespread of these scams head-on.

As used by many people, "theory" means "hypothesis", therefore a
guess that can be disregarded. But "theory" in science actually refers to any
coherent, organized body of ideas. The structural integrity of the Sears Tower was
calculated using "stress theory" but nobody believes the Sears Tower was built
using guesswork or unproven hypotheses. The portion of music training that describes
notation, chords, and harmony is called "theory" although its basic ideas have
been highly refined and workable since before Bach.

If evolution really happened, then its opponents are wrong, and they will have to deal
with the religious and ideological problems that raises. But that's not science's problem.
Opponents of evolution created their own problems and they will have to solve them. This
is one of the meanings of the dictum "Science is Value-Neutral"; if scientific
findings conflict with your value system, your value system must be wrong. This is
anything but a "value-neutral" stance; it's a strident assertion that we are
more likely to find the truth by following the evidence honestly than by tailoring
findings to fit a preconceived belief system.

Discovery of Evolution

Evolution by natural selection was discovered by Charles Darwin and Alfred Russell
Wallace. Darwin had been naturalist on the famous Beagle expedition in the 1830's.
He mulled over his observations for a quarter-century and was just about to publish when
he got a letter from Wallace outlining the theory. What could have been a seriously nasty
priority squabble became a model for scientific cooperation. Darwin, as senior scientist,
got most of the credit at the time (and took most of the heat) but Darwin worked to ensure
that Wallace got a fair hearing for his ideas. Wallace, for his part, actively defended
Darwin and his writings. Historians now give both scientists equal credit for the
discovery.

The interactions of science and society following the discovery of evolution are
fascinating, complex, and far-reaching. They are discussed in more depth at these two
sites:

The Geologic Record

The geologic record contains the history of life on earth. The overall conclusions we
can draw from it are:

The physical evidence preserved in the rocks records mostly small-scale, gradual
processes. Sudden and violent events do occur but are rare, and they leave absolutely
unmistakeable evidence that is mostly lacking from the rocks. The idea that Earth's
history is dominated by gradual processes is a finding based on physical evidence,
not an assumption.

The record of life preserved in fossils shows a gradual increase in complexity with
time.

Contrary to widespread misconception and even outright denial by opponents of evolution,
fossil forms intermediate between major groups are well documented. We have
intermediate forms between reptiles and birds, reptiles and mammals, amphibians and
reptiles, fishes and amphibians.

Over most of its history, life on Earth was simple. Only in the last 15 per cent (700
million years) of Earth's history do really complex orgainsms occur.

Observational Evidence

Sagan uses the Heike crabs of Japan as an example of unconscious artificial selection
by humans. We can see that there are several different kinds of natural and artificial
selection:

Deliberate selection for desirable traits by humans. We only learned to do this
systematically about 1700, and only learned why it worked after genetics was discovered in
the mid-19th century.

Unconscious selection for desirable traits by humans. We've been doing this for
thousands of years. The cow that gives lots of milk is kept, the rest are slaughtered. The
seed that gives high yields is saved and the rest eaten. But we didn't know how to breed
animals and plants for specific traits until recently. But even unintentional selection
can go a long way. Corn has been so changed by humans that it can no longer reproduce on
its own, and its natural ancestor is difficult to identify (it's generally thought to be a
wild Mexican grain called teosinte.) Would you identify a chihuahua as having
derived from a wolf? For that matter, would you identify a chihuahua and a Saint Bernard
as members of the same species if you had never seen dogs before?

Unconscious and unintentional selection by humans. This is "artificial" only
in the sense that humans are involved; otherwise it's just natural selection. The Heike
crabs are an example. Nobody intended to breed samurai crabs, or even knew it was going
on. I suspect the crabs already looked pretty Japanese long before the Battle of
Danno-Ura, and the myth arose afterward as a picturesque way of explaining the crabs and
commemorating the battle.

Natural selection with no human selection at all. Examples of this have been observed
even in historic times. Humans as change agent have triggered many changes without doing
any selecting themselves. Our habitat changes select for generalist organisms and against
organisms that require highly specific habitats. Humans also get selected; when disease
organisms kill their human hosts too efficiently, both the organism and the humans lose
their chance to reproduce. Evolution selects for more moderate pathogens and more
resistant humans. Measles was only moderately serious to Europeans but lethal to Native
American populations that had never encountered it before. Syphilis may have travelled in
the other direction and was much more lethal to the first Europeans who got it than it is
now.

We have not been observing long enough to witness the appearance of entirely new
species but we have certainly observed enough important pieces of the evolutionary
mechanism to be reasonably sure how it works:

Artificial selection has produced organisms radically different from their natural
state. An extraterrestrial biologist would probably not hesitate to call retrievers and
poodles distinct species, or at the very least, subspecies. True, poodles and retrievers
can interbreed, but so can dogs, wolves, and coyotes, which are considered separate
species.

Natural selection has resulted in dramatic changes in natural populations. The classic
example is the European peppered moth. This moth occure in a light and dark form. As
industrial pollution darkened surfaces in the 19th century, the dark form of this moth
rapidly went from a few per cent of the population to dominant. As the environment began
to clean up following the decline of coal as a fuel, the light form became more abundant
again.

Microorganisms and viruses change with dazzling speed. We have to get flu shots every
year because flu viruses mutate so quickly. Bacteria have evolved resistance to
antibiotics in just a few decades.

Mutations

Most popular discussions of evolution suggest that mutations, or genetic changes, occur
and then an organism evolves to a new form. But if you randomly tinker with the engine of
your car or some electronic component in a computer, you will virtually certainly make
things worse, not better. Similarly, most organisms are well-adapted to their environment;
any genetic change is almost certain to make them less well-adapted, not more.

If the chances of a beneficial mutation happening are very tiny, nature has a huge
number of organisms to work with. If the chance of a beneficial mutation occurring are one
in billions, but there are trillions of organisms during the lifetime of a species, some
will win the lottery.

More likely, though, is that mutations serve as genetic contingency plans. Fins that
can double as crude legs may make you less agile in the open water, but are just the
ticket if you find yourself trapped in a shrinking pond. When the environment changes,
some mutations that had been harmful might become advantageous. Likewise, when organisms
move into new environments (say colonize remote islands), their mutations may become
useful or at least harmless. Island organisms, free of competition, tend to radiate
rapidly into all kinds of specialized forms. They also tend to be easy prey for the more
generalized organisms from the continents. That's one reason why humans have deliberately
and unwittingly driven so many island organisms to extinction.

Prebiotic Evolution and DNA

DNA

The hereditary code for humans is contained in the molecule DNA, Deoxyribonucleic
acid. The DNA in humans contains a few billion pairs of molecules arranged in a spiral
ladder form. An atom is about 10-8 centimeters in diameter, and each rung on
the ladder is a few atoms high, so the total length of human DNA in a single cell is about
a meter. Most cells are microscopic; the DNA fits in such a tiny space because it is
tightly coiled. The act of uncoiling DNA, splitting it, replicating it and separating the
strands without tangling in such a tiny space is mind-boggling. Ever put your clothes on
in a sleeping bag? Imagine taking raw wool or cotton, spinning it into thread, weaving the
cloth, sewing it into clothes, and putting them on in the sleeping bag. That's what
replicating DNA amounts to.

A human body contains about 20 trillion cells. The total length of DNA in a human body
is thus 20 trillion meters, or twenty billion kilometers, the circumference of the orbit
of Pluto. The DNA in a human body would wrap around the Solar System.

Prebiotic Evolution

The basic molecules of organic chemistry are easily made

The classic Miller-Urey experiment of the 1950's showed that it was easy to create
organic chemicals like amino acids from inorganic ingredients. Many of these molecules
have been detected in interstellar space. Some scientists believe that inorganic
precursors of life arrived on Earth ready-made during meteor impacts. The ease of creating
organic molecules leads some biologists to believe that life is all but inevitable on any
world with suitable physical conditions.

The first self-replicating molecule was almost certainly not DNA

Your cells contain a single-strand self-replicating molecule called RNA (ribonucleic
acid). Some viruses contain only RNA. It is much more likely that RNA evolved before DNA,
and quite possible that something simpler preceded RNA. The first self-replicating
molecules might have been very simple.

DNA assembles from simpler materials all the time

When a DNA molecule splits and replicates, where does the missing half come from?
It comes from the simple organic molecules in your cell fluids. When the correct molecule
drifts into contact with the DNA, it is attached by the DNA editing molecule. None of this
is done consciously. The fact that the mating hald of a DNA molecule is already there is
irrelevant; you could pile lumber next to a half-built house with all the necessary tools
and blueprints nearby and it would never spontaneously assemble into a house.

Randomness, Order and Evolution

Few things about evolution cause as much misunderstanding as the use of terms like
"random". To most people, "random" means without order or purpose, but
it has quite a different meaning in science. Consider a couple of examples:

Are the following letter sequences random: crvn, smrt, vrlo, gdje, trg?
The look random enough; most don't even have vowels. That's a problem in English, not in
Serbo-Croatian. The words mean, respectively, red, death, very, where and town square. Moral:
the fact that something looks random doesn't mean it is. It may convey meaning in a way
you don't understand.

Is the following number sequence random: 592653589793238462643383279?
It not only looks random: it is random. This particular number sequence has passed
every test for randomness mathematicians have ever used on it. But lacking in meaning? No.
These are the digits of pi beginning with the fourth decimal place. Not only is this a
very meaningful number sequence, it is absolutely determined: the trillionth digit of pi
is absolutely fixed, even if we haven't yet computed it.

The Scientific Meaning of Random

The trillionth digit of the fraction 1/3 in decimal form is 3. The only known way to
predict the trillionth digit of pi is to calculate it. You can guess the next decimal
digit of 1/3 with 100 per cent accuracy. If you try to predict the next digit of pi your
overall accuracy is ten per cent. So one very important meaning of "random" is
that something cannot be predicted with better accuracy than that predicted by
statistics. This unpredictability can occur even in something as precisely defined as
pi.

One important reason why things may be unpredictable is lack of information. If you
pick a date in the past or future and guess the positions of the Moon and planets, you
will do no better than random guessing, even though the positions of the planets can be
foretold with high accuracy. Since you don't carry formulas for the motions of the planets
in your head, your guesses will have no accuracy. I omit the Sun from this discussion
because you can guess the Sun's position from the date.

One approximation to pi is 22/7 = 3.142. A much better one is 355/113 = 3.1415929. But
note that in each case the fractions have as many digits as the accuracy they achieve. It
is just as much work to write or remember the fractions as it is simply to remember pi to
the same accuracy. If you had absolutely precise information about the forces on a coin
and the surface it lands on, you could, in principle, predict how a coin toss will turn
out. It would take far more effort than simply flipping the coin. One other definition of
randomness is that it takes as much information or effort to describe an event fully as
it does simply to produce the event itself. In other words, the actual event is its
own simplest description.

In addition, some things are inherently unpredictable. We can predict climate
(the overall physical conditions on Earth) with ever-improving accuracy, but weather
forecasts become increasingly unreliable after only a few days. We can predict general
trends during an El Nino season, but whether it will snow Christmas Eve in Green
Bay is still unpredictable. And mounting evidence suggests it may never be
possible; that tiny uncertainties in measurement now may result in increasingly great
differences as time goes by. Systems of that sort are called chaotic. They are
completely governed by the laws of physics, but incomplete information prevents us from
achieving completely accurate long-term predictions.

We can see easily how these concepts apply to evolution: biological systems are far too
complex to describe mathematically, we have incomplete information, and significant events
like climate change or asteroid impact are unpredictable.

Can Order Arise Naturally?

The Second Law of Thermodynamics is often paraphrased as "things always go from
bad to worse." Most popular descriptions describe it as "disorder in the
Universe is always increasing." The law is often illustrated by dumping a jigsaw
puzzle on the floor and imagining the likelihood of it spontaneously self-assembiling. But
the actual concept at the core of the Second Law is something called entropy. In
discussing order and evolution, the only concept that is relevant at all is entropy.
Intuitive notions of whether one outcome is more disorderly than another are of no
relevance whatsoever. Entropy often corresponds to our intuitive notions of disorder,
but not always.

For example, when you assemble the jigsaw puzzle, you are reducing the disorder in that
system. But, at the same time, you are expending energy to move the pieces around and
perform the mental tasks needed to solve the puzzle. Complex organic molecules you ate a
few hours ago are broken down into simpler molecules, some of which are exhaled as carbon
dioxide and water vapor. Liquid water in your body is vaporized as perspiration. The
puzzle as a whole has gone to a state of lower entropy, but the entire system - you, the
puzzle, your food, the surrounding atmosphere, has gone to a state of higher
entropy.

It is possible for water to run uphill, over rocks in a stram perhaps, if it's first
picked up speed by falling. Similarly, entropy can decrease locally, if entropy in a
larger sense increases to make up for it. Spontaneous order arises all the time in nature,
but always as the result of a larger increase in entropy somewhere else.

Although we speak of random motions of molecules in the origin of life, we mean random
in the sense of statistically complex. Chemical reactions are not random. For
example, if we had a bucket of dimes and pennies and dumped them on the floor, the chance
of their arranging like this would be negligible:

It's easy to form salt crystals naturally: just let a container of salt water
evaporate. The chances of sodium and chlorine atoms arranging by chance in a rigidly cubic
alternating array is zero, but it doesn't happen by chance. The sodium atoms have a
positive charge, the chlorines a negative charge. The opposing charges attract and like
charges repel. The chance of their arranging this way is virtually 100 per cent.

Some people have attempted to calculate the likelihood of forming complex organic
molecules as if the molecules assemble by random addition of components. Of course the
probability of forming a molecule that way is vanishingly small because molecules don't
form like that. The missing half of a replicating DNA molecule spontaneously assembles
from simple organic molecules in the cell (see above). A simple-minded probability
calculation would put the probability at near zero; actually it is virtually 100 per cent.

Two General Principles

No discussion of order and evolution has any value unless it includes a rigorous and
accurate discussion of entropy. Entropy, not intuitive ideas about order or disorder, is
the only thing that counts.

No treatment of chemical reactions as random events has any value. Chemical reactions
are not random.

Artistic Conventions

This video is an excellent place to observe the role of artistic conventions in
portraying science. Some of the conventions used in this video include:

Anthropomorphism

Attributing human characteristics to non-human entities. For example, the DNA copying
enzyme "knows" how to do its task.

Accelerating Events

The film of lymphocytes devouring bacteria is speeded up. Even more, the animation of
evolution is speeded up by a factor of bilions. It creates the impression that evolution
was more linear and much faster than it was.

Picturing the invisible

What does a strand of DNA "look" like? It's narrower than a wavelength of
light; a light wave won't reflect off a strand of DNA any more than a huge ocean wave will
bounce off a pebble. Depictions of atoms model most of their important physical properties
in ways that aid visualization, but we have to remember that they are visualizations. At
scales smaller than the atomic, matter takes on complex properties of both particles and
waves, and no single image will accurately represent matter completely. We can emphasize
one feature or another, but not every property at once.

Bringing the past to life

What color were dinosaurs? What sounds did they make? We simply don't know. Artists can
give greater realism to images of the past by including plausible guesses about such
details, but it's easy to forget that they are guesses.

What if?

Artists can show images of hypothetical planets, such as the one that closes the video.
The best of these are based on careful science and stand up very well. Stanley Kubrick's 2001:
A Space Odyssey was made before the first manned lunar landings but is so accurate
that it set the standard for all future space films. Other images are more hypothetical
and not as likely to be verified in the near future. It can be easy to forget that these
images are just imaginary. They can even show us things that never were, say a
world where Rome never fell or the Nazis won World War II.

Significant Points

Refer to the links above for some of these items:

What role did each of these people play in the development of evolution:

Linneaus

Lamarck

Hutton

Lyell

Darwin

Wallace

Mendel

What was Darwin doing on the Beagle?

How did Darwin and Wallace react to their simultaneous discovery of evolution?

What are some of the principal ideological abuses of evolution?

Why do fundamentalists reject the idea that evolution is "just God's way of
creating life?"

Where does the term "fundamentalism" come from?

What happened during the Scopes Trial?

How does evolution by natural selection work?

What does the geologic record tell us about conditions on Earth and the evolution of
life?

Describe the structure of DNA

What's the popular view of mutations? Why is it wrong? How do mutations operate?